Indeed a great adventure. I was in Mongolia in 2010 and did a mix of northern route with the middle route, trying to avoid the main roads.. it was wonderful. This summer we're going there again :)
If you wanted to register the bikes.. would it have been easy or complicated? I would like to make a trip from UB to north of Mongolia and then Russia and then back to Mongolia. Would it be possible with such a bike? I know that in Mongolia everybody ride them, but in Russia? (Altai) What to do if the bike crash there.